Do all central air conditioners have the same condensors

No. Different AC units have different sized condensers to meet the cooling load of the home. There are also single and two stage compressors. The two stage compressors are a bit more expensive, but they achieve higher efficiency.

There likely are differences between different brands and models such as features, warranty, noise level, and so on.

To keep legal happy, let me just say that I am not an HVAC contractor, and you should never even look at your furnace without having a qualified, liability accepting HVAC contractor present. To keep sales happy, let me just say that you can find an HVAC contractor that's happy to take your money here: http://www.furnacecompare.com/perl/find_contractors.pl.

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